A basic concept in imaging in general, and digital imaging in particular is the resolution, i.e., the ability to distinguish small details in a captured image. Resolution can relate to horizontal details, vertical details or both. The resolution primarily depends on the number of sensor cells in the sensor of a digital camera, and on the number of picture elements pixels) in the resulting image.
An important aspect of resolution is edge detection and enhancements. If edges are detected they can be enhanced and viewed more clearly, thus increasing resolution. Consider for example FIG. 1A and FIG. 1B. In FIG. 1A, the lines blur at about 500 lines per image, wherein in FIG. 1B, which presents higher resolution, the lines blur at almost 600 lines per image.
Color video sensors usually comprise pairs of quadruples of cells, each quadruple comprising a cyan cell, a yellow cell, a magenta cell and a green cell, arranged as a 2×2 matrix, wherein the order of the green cell and magenta cell changes between neighboring quadruples. Sensors may use one of two operation modes, being Line Addition Mode on, and Line Addition Off mode. In Line Addition On mode, which is more commonly used since it provides wide dynamic intensity range, every pixel in every line in one of the output fields of the resulting image is a sum of two vertically adjacent pixels in the sensor, so access to the direct value of each sensor cell is disabled. In Line Addition Off mode, the row value of each sensor cell is available. The intensity values of the sensor cells, which carry the edge information, are output to a display device as Y component, also known as the luminance component, and the color information is output as a chrominance channel. The Y component is determined by averaging neighboring sensor cell values, activating edge detection filters on the resulting values and adding the edge information to the values. The resulting values thus present bold edges, but often conceal smaller ones, mainly due to the averaging of values and generating a single pixel out of every four sensor cell values.
There is thus a need in the art for a method for deriving small or subtle edges, both in devices working using the Line Addition On mode and in devices using the Line Addition Off mode. The method and apparatus should be performed in real time environment, so as to enable enhanced resolution video images.